1. Field of the Invention
The present invention relates to apparatus and methods for controlling the atmosphere of substantially sealed food storage chambers.
2. Prior Art
It is known that perishable or oxidizable foods may be preserved more effectively for extended periods in storage if the oxygen and carbon dioxide contents of the atmosphere surrounding such foods are maintained at levels below those normally found in the atmosphere. Food storage systems in which substantially sealed storage chambers are interconnected with various types of burners to remove oxygen, including catalytic burners, and various types of scrubbers to remove carbon dioxide, including charcoal adsorbers, are disclosed in British Pat. No. 457,888 and in the following U.S. Pat. Nos.;
Smith--52,650 PA1 Lindewald--2,789,059 PA1 Bedrosian et al.--3,102,780 PA1 Robinson--3,107,171 PA1 Harvey, Jr.--3,313,630 PA1 Jensen--3,313,631 PA1 Burg--3,400,650 PA1 Jensen--3,451,782 PA1 (1) through the burner, then through an adsorber and then to an air outlet; PA1 (2) through the burner, then through an adsorber and then to the storage area; or PA1 (3) through the burner and directly to the storage area.
When charcoal adsorbers become loaded with carbon dioxide and lose their scrubbing effectiveness, carbon dioxide can be purged from them by blowing ambient air through them. A storage system using two adsorbers alternately connected to a substantially sealed storage chamber has been developed. When one of the adsorbers becomes loaded with carbon dioxide removed from air circulated from the storage chamber through it and back to the storage chamber, the other adsorber is connected to the storage chamber to scrub air from the food storage atmosphere while the first adsorber is purged with fresh air. Similarly, when the second adsorber becomes loaded with carbon dioxide, the purged adsorber is reconnected to the storage chamber to scrub additional air from the storage atmosphere while the second adsorber is being purged. The problem with this type of system is that when an adsorber is reconnected to the storage chamber, fresh air in the reconnected adsorber is introduced into the food storage atmosphere which increases the oxygen content of such atmosphere that is available for stored produce to convert to carbon dioxide, thus accelerating aging of the stored produce.
Lamp, Jr. U.S. Pat. No. 3,445,193 discloses a food storage system using a burner, two adsorbers and an unsealed storage area. According to the Lamp, Jr. system, several different circulations of air may be effected. Air may be drawn from an external atmosphere inlet and blown:
In accordance with the Lamp, Jr. system, high oxygen content and high carbon dioxide content air alternately are introduced into the storage area. When one adsorber is being used the other adsorber is purged with fresh air. However, the Lamp, Jr. patent does not disclose introducing air from a storage area into a purged adsorber to prevent high oxygen content air from being introduced into the food storage area when the purged adsorber is reconnected to the system.